Watermelon snow, natural sunscreen

SNIPPETS

Watermelon snow, natural sunscreen

In snowy places across the globe, ‘watermelon snow’ forms as the summer sun heats up and melts winter’s leftovers. The colourful snow is made of blooms of algae that thrive in freezing temperatures and liquid water.

When these organisms are exposed to a lot of sun, they produce a natural sunscreen that paints the slopes pink and red. The pigment changes snow’s albedo (proportion of the incident light or radiation that is reflected by a surface) — how much light, or radiation, is reflected back into the atmosphere.

A new study estimates that blooms of snow algae can lead to an albedo decrease of 13% over the course of an Arctic melt season, compared with clean snow. The algae are so ubiquitous that it’s time for climate models to consider their effects on snow and ice melt, the authors concluded.
Joanna Klein

Scales, feathers and hair have a common ancestor

Reptiles have scales. Birds have feathers, and mammals have hair. Scientists long believed these features appeared independently, but a new study suggests that they originated in a common ancestor. The reptilian creature, living some 320 million years ago, eventually gave rise to dinosaurs, birds and mammals. The animal is thought to have been covered in scalelike structures, which developed from placodes — tiny bumps of thick tissue found on developing embryos even today. Scientists had observed placodes on the embryos of birds and mammals, where they develop into feathers and hairs, but never on a reptilian embryo.

Now biologists at the University of Geneva have discovered the anatomical structures in bearded dragon lizards, Nile crocodiles and corn snakes, as well as mice. “When we investigated normal snakes, normal crocodiles and normal lizards, we found placodes everywhere,” said Michel C Milinkovich, who led the research.He and his colleagues conclude that birds, mammals and reptiles inherited placodes from the same ancestor. So why did no one find placodes in reptiles before?

The structures are extremely difficult to spot in developing reptiles, appearing for a brief period of about 12 hours. And the tissue pops up in different locations, depending on the species. “If you look too early, you see nothing,” Michel said. “If you look too late, it’s already a scale.”
Nicholas St Fleur

Saiga antelopes’ mysterious epidemic

Within a few weeks in May 2015, a mysterious illness killed more than 200,000 endangered saigas in Kazakhstan, more than 60% of the species. This spring, scientists and conservationists around the world waited anxiously to see whether the die-off would be repeated. There has been no similar catastrophe this year, they report; indeed, an April census revealed that these rare antelopes are making modest gains.

Stephanie Ward of Britain’s Royal Society for the Protection of Birds, a partner in the conservation programme, attributed the population growth to the Kazakh government’s effort to combat poaching for meat and male saiga horns, which are prized in Chinese traditional medicine.

Researchers have pinned last year’s die-off on Pasteurella multocida, a bacterium that commonly causes disease in water buffalo, cattle and bison. But the bacteria naturally occur in the antelopes, and what caused them to become so virulent is unclear.